The invention relates to an apparatus for making plastic bags.
There has been commercially available an apparatus for making plastic bags 2 from a web material 4 comprising two or more layers of plastic film, as shown in FIG. 11. The apparatus includes feeding means by which the material 4 is intermittently fed for a length along a longitudinal feeding path. The material 4 is heat sealed by heat seal means longitudinally and widthwise of the material 4 whenever intermittently fed and temporarily stopped so that heat sealed portions 5 can be formed longitudinally and widthwise of the material 4. In two rows production, the material 4 may be slitted by slitting means along a slit line 6. In case of shaped bags 2 each of which has opposite sides curved convexly or concavely, the apparatus is arranged to successively make plastic bags 2 with wastes 8. Each of the wastes 8 has upstream and downstream edges 10 and 12. In general, the material 4 is totally cut by suitable cutting means along the upstream and downstream edges 10 and 12 of waste 8 whenever intermittently fed and temporarily stopped. The wastes 8 are therefore brought into existence one by one or two by two by making shaped bags 2. The waste 8 may be called a waste material or scrap.
Under the circumstances, a hole is usually formed under the feeding path of material so that the wastes can be dropped down through the hole to be removed. However, the wastes 8 can neither always be dropped down nor removed even if the material 4 is totally cut. The plastic bags 2 and the wastes 8 may adhere to each other by reason of certain factor such as static electricity, to be fed as they are. The wastes 8 must therefore be removed later and manually by operator from the plastic bags 2, taking labours and times. In addition, as to the hole through which the wastes 8 are dropped down, it is required to change the size of hole when changing the size of plastic bag 2 and waste 8.
It is therefore an object of the invention to provide a new and improved apparatus for making plastic bags from a web material comprising two or more layers of plastic film, to overcome the above problems. The apparatus including feeding means by which the material is intermittently fed for a length along a longitudinal feeding path, to successively make plastic bags with wastes, each of the wastes having upstream and downstream edges.
Another object of the invention is to provide the apparatus in which the wastes can be removed automatically and reliably, without adhering to the plastic bags.
According to the invention, the apparatus comprises partially cutting means disposed at a first station predetermined along the feeding path. The material is partially cut by the partially cutting means along the upstream and downstream edges of waste whenever intermittently fed and temporarily stopped.
The apparatus further comprises waste removing means disposed at a second station predetermined downstream of and at a distance from the first station. The waste reaches the second station when the material is intermittently fed again after partially cut by the partially cutting means.
In addition, the apparatus comprises discharge means disposed at a third station predetermined downstream of and at a distance from the second station. The material reaches the third station when intermittently fed again after partially cut by the partially cutting means. The material is pulled and torn by the discharge means from the downstream edge of waste to be discharged by the discharge means as a plastic bag, the waste being pulled, torn and removed by the waste removing means from the upstream edge of waste, after the waste reaches the second station and the material reaches the third station.
In a preferred embodiment, the partially cutting means comprises Thomson blade means opposed to the material. The partially cutting means further comprises drive means by which the Thomson blade means is moved toward the material so that the material can be partially cut by the Thomson blade means along the upstream and downstream edges of waste.
The Thomson blade means has micro depressions formed and spaced from each other along the cutting edge thereof to leave micro joints formed and spaced from each other along the upstream and downstream edges of waste. The micro joints make the material partially cut. The material and the waste are kept connected with each other by the micro joints.
The material is partially cut by the partially cutting means to be pulled and torn more easily at the downstream edge than at the upstream edge of waste. The material is first pulled and torn by the discharge means from the downstream edge of waste after the waste reaches the second station and the material reaches the third station. The waste is then pulled and torn by the waste removing means from the upstream edge of waste.
The waste removing means comprises upper and lower rotating members disposed on upper and lower sides of the feeding path. The waste removing means further comprises drive means by which at least one of the upper and lower rotating members is moved toward the waste so that the waste can be sandwiched between the upper and lower rotating members. In addition, the waste removing means comprises drive means by which at least one of the upper and lower rotating members is rotated at a considerable speed so that the waste can be pulled and torn by the upper and lower rotating members.
The discharge means comprises upper and lower belts between which the material is directed and sandwiched to be pulled and torn by the upper and lower belts.
In other embodiment, the waste is held by the waste removing means after reaching the second station so that the material can be pulled and torn by the discharge means from the downstream edge of waste. The waste is then pulled and torn by the waste removing means from the upstream edge of waste.
The waste removing means may comprise drive means by which at least one of the upper and lower rotating members is moved toward the waste so that the waste can be sandwiched between and held by the upper and lower rotating members after reaching the second station.
In other embodiment, the waste removing means comprises upper and lower fingers disposed on upper and lower sides of the feeding path. The waste removing means further comprises drive means by which at least one of the upper and lower fingers is moved toward the waste so that the waste can be sandwiched between and held by the upper and lower fingers after reaching the second station. In addition, the waste removing means comprises drive means by which the upper and lower fingers are moved in a direction so that the waste can be pulled and torn by the upper and lower fingers.
In other embodiment, the discharge means comprises drive means by which the upper and lower belts are driven at a first speed. The waste removing means comprises drive means by which at least one of the upper and lower rotating members is moved toward the waste so that the waste can be sandwiched between the upper and lower rotating members at the same time as the material is sandwiched between the upper and lower belts. The waste removing means further comprises drive means by which at least one of the upper and lower rotating members is rotated at a second speed lower than the first speed so that the material is pulled and torn by the upper and lower belts, while the waste is pulled and torn by the upper and lower rotating members, by means of a difference in speed between the upper and lower belts and the upper and lower rotating members.
In other embodiment, the apparatus comprises partially cutting means combined with totally cutting means. The material is partially cut by the partially cutting means along the upstream edge and totally cut by the totally cutting means along the downstream edge of waste whenever intermittently fed and temporarily stopped.
The apparatus further comprises discharge means disposed downstream of and at a distance from the partially and totally cutting means. The material is discharged by the discharge means as a plastic bag after partially and totally cut. The waste then reaches the discharge means when the material is intermittently fed again, to be pulled, torn and removed by the discharge means from the upstream edge of waste.
The partially cutting means comprises drive means by which the Thomson blade means is moved toward the material so that the material can be partially cut by the Thomson blade means along the upstream edge of waste. The micro joints make the material partially cut. The waste is kept connected with the material by the micro joints.
The discharge means comprises upper and lower belts, the material being directed and sandwiched between the upper and lower belts to be discharged by the upper and lower belts. The waste is then directed and sandwiched between the upper and lower belts to be pulled, torn and removed by the upper and lower belts. Stop means is incorporated into the upper and lower belts so that the waste can strike against the stop means for dropping from the upper and lower belts.